In the fall of 2008, filmmaker Dana Adam Shapiro's friends began splitting up in droves (four in one month alone), and the bachelor wondered: Can I glean anything useful from their heartbreak? "In driver's ed, they show films that end in car wrecks, and you learn what not to do because you don't want to wind up like that," says Shapiro. "I figured knowing the things that destroy a marriage would give me a better chance of having a successful one someday. But I couldn't interview my friends--they needed support, not a voyeur." So he spent four years questioning hundreds of divorced strangers, and compiled their insights in the new book You Can Be Right (Or You Can Be Married). His top five lessons:

#1. It's about small-scale romance. "One woman told me that keeping a marriage sexy isn't about big gestures like expensive gifts or trips--it's daily romance. That means eating a pizza together on the couch, or sitting on the couch stroking your wife's hair. Couch love, basically."

#2. The wooing never stops. "One thing I could trace throughout all the failed marriages was complacency. The eternity that's implied when you wed can lead you to feel like you don't have to try anymore. One guy said you have to re-earn your partner's love every year. Unconditional love is for your children."

#3. You're not fighting about what you think you're fighting about. "Those little issues we gripe over--the toilet seat being up or hair clogging the shower drain--are just things we use to go after each other. No one really cares that much about the toilet seat. It's that they ask repeatedly and are ignored."

#4. Sex is more than sex to him. "A startling number of men never received oral sex from their wives. For men, oral sex can be very intimate, and not having it genuinely makes them feel rejected. It creates a cycle of withholding where they say, 'If you're not going to do that, then I'm not going to do this' that affects other areas of the relationship."

#5. You can handle the truth. "One man's first wife didn't know for years that he was a cross-dresser. When he started dating his new wife, he said if she couldn't accept it, they wouldn't work. I remembered that when I was on a date with a vegetarian and almost didn't order a steak. But I thought, If eating meat is going to be a problem, we should know now. Being honest up front makes it easier in the long term."